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Differential attenuation of somatovisceral and viscerosomatic reflexes by diazepam, phenobarbital and diphenylhydantoin

1975; Elsevier BV; Volume: 14; Issue: 7 Linguagem: Inglês

10.1016/0028-3908(75)90057-x

1873-7064

Walter Schlosser, S. Franco, E.B. Sigg,

Transcranial Magnetic Stimulation Studies

In the chloralose-anaesthetized cat, stimulation of forelimb cutaneous afferent nerves evoked a response in the preganglionic splanchnic nerve, consisting of a short duration spinal reflex followed by a supraspinal component of longer duration. Diazepam (0·1–1·4 mg/kg, i.v.) markedly attenuated the supraspinal reflex but had a considerably lesser effect on the segmental response. On the other hand, diphenylhydantoin (10–40 mg/kg, i.v.) reduced predominantly the spinal component, whilst the supraspinal reflex was frequently enhanced after the initial dose of 10 mg/kg. This effect of diphenylhydantoin on the spinal reflex was direct, since it also occurred in the spinal cat. Phenobarbital (10–40 mg/kg, i.v.) was approximately equally potent in reducing both the spinal and supraspinal reflex. Visceromotor reflexes were markedly depressed by very small doses of diazephm (0·001 mg/kg, i.v.) and by larger doses of phenobarbital (10–20 mg/kg, i.v.). Diphenylhydantoin, although reducing this reflex, did not completely block it at the highest total dose tested (40 mg/kg, i.v.). The results indicate that the three CNS depressants differentially affect the spinal and supraspinal components of the somatosymphetic reflex. Furthermore, the three drugs also differ quantitatively from each other in depressing the spino-bulbo-spinal transmission of the viscerosomatic reflex.